In situ geophysical sensing apparatus method and system

ABSTRACT

An apparatus for in situ geophysical sensing includes a sensor for measuring geophysical data and a liquid absorbent member connected to the sensor that expands in response to contacting a liquid and thereby physically couples the sensor to a local sensing environment. The liquid absorbent member may be formed of beads or pellets or powder that includes a liquid absorbent material. The liquid absorbent member may also include a soluble binding agent for binding the beads or pellets or powder into an integral member such as a casing for containing the sensor. A method and system corresponding to the apparatus are also described herein. The apparatus, method and system described herein may be used to improve borehole sensor data quality without adding significant complexity to the borehole sensor deployment process.

BACKGROUND

1. Technical Field

Embodiments of the subject matter disclosed herein generally relate tothe field of seismic sensing. In particular, the embodiments disclosedherein relate to devices, methods and systems for in situ boreholecoupling for geophysical sensing applications.

2. Discussion of the Background

Seismic sensors are often deployed in wells for geophysical dataapplications. The sensors need to make firm contact with the walls ofthe well in order to accurately record seismic data. However, thesensors often suffer from substandard coupling to the walls of theborehole resulting in poor data quality. Packing suitable fillermaterial between the sensors and the walls of the well without leavingvoids is difficult—particularly for applications where the boreholesensors are stacked. For example, grout densities are often too low totravel down a borehole and fully encompass a sensor. In such cases alarger borehole may be cut and a hose or pipe used to travel past one ormore sensors and deposit grout from the bottom up. This may requirespecialized grout pumping equipment and a larger borehole. However, evena bottom up approach may leave unwanted gaps in the filler material.

Commonly assigned U.S. patent application Ser. No. 12/171,135, which isincorporated herein by reference, describes an alternative solutionwhere an inflatable bladder can be used to fill in the space between thesensor and the borehole. While the quality of the geophysical datagenerated may be improved, implementing such a solution adds complexityto the borehole sensor deployment process.

What is needed is a borehole coupling solution that does not addsignificant complexity to the borehole sensor deployment process.

SUMMARY

As detailed herein an apparatus for in situ geophysical sensing includesa sensor for measuring geophysical data and a liquid absorbent memberconnected to the sensor that expands in response to contacting a liquidsuch as water and thereby physically couples the sensor to a localsensing environment. The liquid absorbent member may be formed of beadsor pellets or powder comprising the liquid absorbent material.

In certain embodiments, the liquid absorbent member comprises a solublebinding agent for binding the beads or pellets or powder into anintegral member such as a casing for containing the sensor. In otherembodiments, the liquid absorbent member is coated with a soluble layerfor temporary isolation of the liquid absorbent material from liquidthat is in contact with the liquid absorbent member.

In some deployments, water may be naturally occurring within theborehole sensing environment. In other deployments, a borehole may befilled with water, some other liquid, or slurry in order to activateexpansion of the liquid absorbent member.

A method and system corresponding to the above apparatus are alsodescribed herein. The apparatus, method and system described herein maybe used to improve borehole sensor data quality without addingsignificant complexity to the borehole sensor deployment process.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute apart of the specification, illustrate one or more embodiments and,together with the description, explain these embodiments. In thedrawings:

FIG. 1 is a perspective schematic depicting a survey environment whereinan array of expandable geophysical sensors may be deployed;

FIG. 2 is an exploded perspective view drawing depicting a firstembodiment of the expandable geophysical sensor;

FIGS. 3 a and 3 b are side view drawings depicting deployment of thefirst embodiment of the expandable geophysical sensor within a downholepipe;

FIG. 4 is a flowchart diagram of an in situ geophysical sensing method;

FIGS. 5 a and 5 b are side view drawings depicting deployment of asecond embodiment of the expandable geophysical sensor within a downholepipe; and

FIG. 6 is a schematic block diagram of an in situ geophysical sensingand processing system.

DETAILED DESCRIPTION

The following description of the exemplary embodiments refers to theaccompanying drawings. The same reference numbers in different drawingsidentify the same or similar elements. The following detaileddescription does not limit the invention. Instead, the scope of theinvention is defined by the appended claims.

Reference throughout the specification to “one embodiment” or “anembodiment” means that a particular feature, structure or characteristicdescribed in connection with an embodiment is included in at least oneembodiment of the subject matter disclosed. Thus, the appearance of thephrases “in one embodiment” or “in an embodiment” in various placesthroughout the specification is not necessarily referring to the sameembodiment. Further, the particular features, structures orcharacteristics may be combined in any suitable manner in one or moreembodiments.

As detailed herein, a novel apparatus for in situ geophysicalsensing—referred to herein as an expandable geophysical sensor—includesa sensor for measuring geophysical data and a liquid absorbent memberconnected to the sensor that expands in response to contacting a liquidsuch as water and thereby physically couples the sensor to a localsensing environment.

FIG. 1 is a perspective schematic depicting a survey environment (100)wherein an array of expandable geophysical sensors (110) may bedeployed. In the depicted deployment, multiple expandable geophysicalsensors (110) are placed on each cable (112) to form a number of sensorstrings (113) that are weighted with a weight (114) that helps pull theexpandable sensors (110) into place within a borehole (120). A sensorstring (113) may be suspended from a suspension fixture (not shown)located at the top of the borehole (120).

Once in place, the expandable geophysical sensors (110) may expand (notshown) in response to contacting a liquid and thereby physically coupleto the sensing environment that is local to each sensor (110). Cable(112) may facilitate collecting geophysical data from the expandablegeophysical sensors (110) and conducting analysis on that data.

FIG. 2 is an exploded perspective view drawing depicting a firstembodiment (110 a) of the expandable geophysical sensor (110). FIGS. 3 aand 3 b are side view drawings depicting deployment of the firstembodiment (110 a) of the expandable geophysical sensor (110).

As depicted in FIGS. 2, 3 a and 3 b, the first embodiment (110 a)includes a sensor (210), a casing (220), a tip cap (230) with barbs(232), a tip bolt (240) and an end cap (250). The expandable geophysicalsensor (110) expands to improve coupling to a local sensing environment.For purposes of simplicity, the depicted deployment is shown in FIGS. 3a and 3 b within a downhole pipe. However, the expandable geophysicalsensors (110) may also be deployed in a borehole without a pipe in orderto couple directly to the wall of the borehole and the local sensingenvironment.

The sensor (210) measures and provides geophysical data such asseismic-related data or other data associated with a local environment.For example, the sensor may be a geophone, a hydrophone, anaccelerometer, a fiber optic sensor, a temperature sensor, a strainsensor, a pressure sensor, a magnetic sensor, a chemical sensor, a tiltmeter or the like.

The expandable geophysical sensor (110) may include a liquid absorbentmember (215) that is connected to and/or proximate to the sensor (210).For example, the liquid absorbent member (215) may be attached (i.e.,bonded, bolted, etc.), formed around, or deposited onto, the sensor(210), or otherwise arranged so that is proximate to the sensor (210).In one embodiment, the liquid absorbent member (215) comprises twosub-members (e.g., halves) that are mechanically attached to each otherto form the casing (220) and enclose the sensor (210).

The liquid absorbent member (215) comprises a liquid absorbent materialthat expands in response to contacting a liquid and thereby physicallycouples the sensor to a local sensing environment. In one embodiment,the liquid absorbent material is a mined material such as bentonite. Inanother embodiment, the liquid absorbent material is a man-made materialsuch as a super absorbent polymer.

The liquid absorbent member (215) may be formed of beads or pellets orpowder comprising the liquid absorbent material. The liquid absorbentmember (215) may also comprise a soluble binding agent for binding thebeads or pellets or powder into an integral member such as the casing(220). In some embodiments, the liquid absorbent member (215) is coatedwith a soluble layer (not shown) for temporary isolation of the liquidabsorbent material from a liquid that is adjacent to the liquidabsorbent member (215). Using a soluble binding agent or a soluble layermay defer expansion of the liquid absorbent member (215) in the presenceof a liquid and enable unimpeded deployment of the expandablegeophysical sensor (110). In one embodiment, the liquid absorbent member(215) comprises pellets of less than 5 mm in diameter that are coatedwith a food-grade water-soluble binding agent. The use of a food-gradewater-soluble binding agent may minimize the environmental impact of thebinding agent.

In the depicted embodiment, the entire casing 220 is formed of theliquid absorbent member (215). However, in other embodiments the casing(220) is made of a solid material and encompassed partially or wholly bythe liquid absorbent member (215). The casing (220) may contain thesensor when in an unexpanded state (300 a), as shown in FIG. 3 a, aswell as the expanded state (300 b), as shown in FIG. 3 b. As shown inFIG. 2, the casing (220) may include one or more casing sections (222).In the depicted embodiment, the casing sections (222) are split along anaxial dimension to provide a left casing section (222 a) and a rightcasing section (222 b). Each depicted casing section (222 a and 222 b)has casing cavity (224) for receiving and encompassing the sensor 210.

The casing (220) may also include the tip cap (230) and the end cap(250). The tip cap (230) and the end cap (250) may hold the axiallysplit casing sections (222 a and 222 b) in place around the sensor(210). The tip cap (230) and the end cap (250) may also block verticalexpansion of the liquid absorbent member (215) and thereby promotehorizontal expansion of the liquid absorbent member (215) against aborehole wall or downhole pipe (310).

The tip cap (230) may include a number of barbs (232) that providefriction against the borehole wall or downhole pipe (310) and enableplacement of the geophysical sensor (110 a) during deployment.Specifically, the barbs (232) may prevent the expandable geophysicalsensor (110 a) from falling into the borehole or pipe while stillallowing forward movement during deployment. For example, the barbs(232) may enable pushing the expandable geophysical sensor (110 a) witha rod or other insertion tool to a desired position which is held by thebarbs (232) until the liquid absorbent member (215) can expand andcouple the geophysical sensor (110 a) to the borehole wall or downholepipe (310).

The sensor (210) may be connected to a cable (260) that runs verticallythrough the casing (220) and the end cap (250). A cable clamp (270) incombination with the tip bolt (240) may secure the members of expandablegeophysical sensor (110 a) to the cable (260). The cable (260) maycomprise electrically conductive wires that enable uphole communicationof the geophysical data provided by the sensor (210). The cable (260)may also facilitate insertion of the expandable sensor (110) into a hole(312). FIG. 3 b illustrates the liquid absorbent member 215 in anexpanded state, ensuring good coupling with the walls of the pipe 310.In one application, water or other liquids naturally occurring in thewell are absorbed by member 215. In another application, water oranother liquid is poured from the surface into the well in order to beabsorbed by member 215.

FIG. 4 is a flowchart diagram of an in situ geophysical sensing method(400). As depicted, the method (400) includes boring (410) one or moreholes, inserting (420) one or more expandable sensors (110), waiting(430) for a liquid absorbent member to expand, measuring (440)geophysical data, collecting (450) the geophysical data, processing(460) the geophysical data and analyzing (470) the geophysical data.

Boring (410) one or more holes may include using hole boring equipmentto create an array of holes that are strategically placed to collectgeophysical data.

Inserting (420) one or more expandable sensors (110) may include pushingor lowering one or more expandable geophysical sensors (110) into eachhole created by the boring operation (410). Inserting (420) may alsoinclude ensuring that the expandable geophysical sensors (110) come incontact with a liquid such as water. For example, in some deploymentswater may be naturally occurring within the borehole sensing environmentwhile in other deployments, a borehole may be filled with water, aslurry, or another liquid, (either before or after insertion of thesensors (110)) in order to activate expansion of the expandablegeophysical sensors (110).

Waiting (430) for a liquid absorbent member to expand may include havinga knowledge of the expected required expansion time for a particularborehole or pipe size and waiting the prescribed time. The expectedrequired expansion time may be collected experimentally or by modelingthe absorption rate of the liquid absorbent member.

Testing may also be conducted to determine if the liquid absorbentmember has expanded sufficiently to provide physical coupling to theborehole or pipe wall. For example, in one embodiment a test shot isfired to determine the effectiveness of the physical coupling of theexpandable geophysical sensors (110) to the borehole or pipe wall. Inanother embodiment, a cable connected to one or more expandablegeophysical sensors (110) may be pulled with a selected force in orderto determine if the expandable geophysical sensors (110) remain fixed inplace and thereby determine if sufficient physical coupling has occurredwith the walls of the borehole or pipe.

Measuring (440), collecting (450), processing (460) and analyzing (470)geophysical data may include conducting operations typically associatedwith geophysical data applications such as seismic analysis. Forexample, processing (460) may provide an image of a surveyed subsurfacesuitable for seismic analysis.

FIGS. 5 a and 5 b are side view drawings depicting a second embodiment(110 b) of the expandable geophysical sensor (110) deployed within adownhole pipe (310). FIG. 5 a depicts the second embodiment (110 b) ofthe expandable geophysical sensor (110) in an unexpanded state (500 a)while FIG. 5 b depicts the second embodiment (110 b) of the expandablegeophysical sensor (110) in an expanded state (500 b).

As depicted, the second embodiment (110 b) includes a sensor (510), oneor more liquid absorbent members (515), a tip (530), a cap (540) and acable (550). One of skill in the art will appreciate that similar tofirst embodiment (110 a), the depicted second embodiment (110 b) issimply illustrative and that many other embodiments of the expandablegeophysical sensor (110) may be realized that fit within the scope ofthe claims.

In many aspects, the depicted second embodiment (110 b) is very similarto the first embodiment (110 a). For example, similar to the sensor(210) the sensor (510) measures and provides geophysical data such asseismic-related data. Also, similar to the liquid absorbent member (215)the liquid absorbent members (515) comprise a liquid absorbent material(such as bentonite or an absorbent polymer) that expands in response tocontacting a liquid and thereby physically couples the sensor to a localsensing environment.

In other aspects, the depicted second embodiment (110 b) is differentfrom the first embodiment (110 a). For example, in contrast to theliquid absorbent member (215) of the first embodiment (110 a), theliquid absorbent members (515) of the second embodiment (110 b) providephysical coupling without functioning as a casing or enclosure for thesensor (510).

Furthermore, the depicted cable (550) extends upward and downward in thesecond embodiment (110 b) which enables connecting multiple expandablesensors (110 b) together into a sensing string as shown in FIGS. 1 and6. For example, in the upward direction the cable (550) may be connectedto another expandable sensor (110 b) while in the downward direction thecable (550) may be connected to a weight that facilitates keeping thestring of expandable sensors (110 b) taut while lowering the expandablesensors (110 b) into a borehole or pipe.

FIG. 6 is a schematic block diagram of an in situ geophysical sensingand processing system (600). As depicted, the in situ geophysicalsensing and processing system (600) includes deployment equipment (605),an array (610) of expandable sensors (110) connected into sensingstrings (113), a signal source (615), one or more data collectionsdevices (620), data processing equipment (630) and one or more dataanalysis workstations (640). The in situ geophysical sensing andprocessing system (600) facilitates measuring and processing geophysicaldata over a selected geophysical volume (not shown).

The deployment equipment (605) may be used to deploy the sensors (110)of the array (610). The deployment equipment (605) may include holeboring equipment used to create one or more boreholes (120). Theboreholes (120) may be created at selected locations on the surface ofthe geophysical volume in order to strategically cover a geophysicalvolume with the array (610) of expandable sensors (110). In order toachieve vertical differentiation over the geophysical volume, multipleexpandable sensors (110) separated by selected distances may beconnected into sensing strings (113). In order to achieve horizontaldifferentiation over the geophysical volume, the strings (113) may belowered into the created boreholes (120) that are spaced laterally overthe geophysical volume. The boreholes (120) may be located on land or onthe floor of a body of water.

Once in place in the presence of water or another liquid, the expandablegeophysical sensors (110) may expand and physically couple to thespecific selected locations within the geophysical volume and providegeophysical data (not shown) corresponding to those selected locations.The geophysical data may include data recorded in response to a signalgenerated by the signal source (615). For example, the signal source(615) may be a seismic source and the geophysical data may be seismicdata recorded in response to a shock wave generated by the seismicsource.

The geophysical data provided by the expandable geophysical sensors(110) may be collected by one or more data collections devices (620),processed by the data processing equipment (630), and analyzed bygeophysicists or the like at one or more data analysis workstations(640).

The embodiments disclosed herein provide an apparatus, method and systemfor in situ geophysical sensing. It should be understood that thisdescription is not intended to limit the invention. On the contrary, thedescribed embodiments are intended to cover alternatives, modificationsand equivalents, which are included in the spirit and scope of theinvention as defined by the appended claims. Further, in the detaileddescription of the disclosed embodiments, numerous specific details areset forth in order to provide a comprehensive understanding of theclaimed invention. However, one skilled in the art would understand thatvarious embodiments may be practiced without such specific details.

Although the features and elements of the disclosed embodiments aredescribed in particular combinations, each feature or element can beused alone without the other features and elements of the embodiments orin various combinations with or without other features and elementsdisclosed herein.

This written description uses examples of the subject matter disclosedto enable any person skilled in the art to practice the same, includingmaking and using any devices or systems and performing any incorporatedmethods. The patentable scope of the subject matter is defined by theclaims, and may include other examples that occur to those skilled inthe art. Such other examples are intended to be within the scope of theclaims.

What is claimed is:
 1. An apparatus for in situ geophysical sensing, theapparatus comprising: a sensor for measuring geophysical data; and aliquid absorbent member proximate to the sensor, the liquid absorbentmember including a liquid absorbent material that expands in response tocontacting a liquid and thereby physically couples the sensor to a localsensing environment.
 2. The apparatus of claim 1, wherein the liquidabsorbent member is formed of beads or pellets or powder comprising theliquid absorbent material.
 3. The apparatus of claim 2, wherein theliquid absorbent member further comprises a soluble binding agent forbinding the beads or pellets or powder into an integral member.
 4. Theapparatus of claim 1, wherein the liquid absorbent member is coated witha soluble layer for temporary isolation of the liquid absorbent materialfrom the liquid that is adjacent to the liquid absorbent member.
 5. Theapparatus of claim 1, wherein the liquid absorbent member is a casingconfigured to fully enclose the sensor.
 6. The apparatus of claim 5,wherein the casing comprises a plurality of casing sections that aresplit along an axial dimension.
 7. The apparatus of claim 5, wherein thecasing comprises a tip portion having a tip cap for blocking verticalexpansion of the liquid absorbent material.
 8. The apparatus of claim 5,wherein the casing comprises an end portion having an end cap forblocking vertical expansion of the liquid absorbent material.
 9. Theapparatus of claim 1, wherein the sensor is connected to a cable. 10.The apparatus of claim 9, wherein the cable facilitates insertion of thesensor into a hole.
 11. The apparatus of claim 9, wherein the cableenables uphole communication of the geophysical data provided by thesensor.
 12. The apparatus of claim 9, wherein the cable is connected toanother sensor.
 13. The apparatus of claim 9, wherein the cable isconnected to a weight.
 14. The apparatus of claim 1, further comprisinga plurality of barbs.
 15. A method for in situ geophysical sensing, themethod comprising: providing an expandable sensor including: a sensorfor measuring geophysical data, and a liquid absorbent member proximateto the sensor, the liquid absorbent member comprising a liquid absorbentmaterial that expands in response to absorbing a liquid and therebyphysically couples the sensor to a local sensing environment; insertingthe expandable sensor into a hole and providing a liquid to theexpandable sensor; allowing the liquid absorbent member to expand inresponse to contacting the liquid and physically couple the sensor to alocal sensing environment; and measuring geophysical data with theexpandable sensor.
 16. The method of claim 15, further comprising:processing the geophysical data to determine an image of a surveyedsubsurface.
 17. The method of claim 15, further comprising: boring ahole for the expandable sensor.
 18. A system for in situ geophysicalsensing and processing, the system comprising: a plurality of expandablesensors placed into one or more holes and expanded to physically coupleto a local sensing environment each expandable sensor including: asensor for measuring geophysical data, and a liquid absorbent memberconnected to the sensor, the liquid absorbent member comprising a liquidabsorbent material that expands in response to absorbing a liquid andthereby physically couples the sensor to a local sensing environment;and data processing equipment for processing the geophysical data. 19.The system of claim 18, further comprising hole-boring equipment forboring the one or more holes.
 20. The system of claim 18, wherein theplurality of expandable sensors are attached to each other along a wireand placed in a single well.